Microsoft has not yet officially responded. But Google's assault comes at a time when the once-omnipotent software giant looks vulnerable. Windows Vista, the most recent version of its operating system, has not been a success. Its forays into Google's main territory, web search and online advertising, have not brought big gains.

Yet it is much too early to count Microsoft out. It recently launched Bing, a new search service, which has been well received. In October, around the time when Google will make Chrome OS available, Microsoft will release Windows 7, the much-improved next iteration of its operating system. The firm is also spending billions of dollars on a “cloud” — a global network of huge data centres — which will rival Google's infrastructure for web-based applications.

Will there be a clear winner? Probably not in the foreseeable future. That is a good thing: the epic fight between the two giants promises to speed up innovation, which is what the recession-bound IT industry most needs.

© The Economist Newspaper Limited 2009